Both mites & fungus can not only be irritating & make your hedgie grumpy, but it can also be fatal if left untreated.
Mites: Mites are generally found in/on the ears, & where the quills cover. You will notice this if the skin is red & or swollen, dry & flakey skin, quill loss, & or open sores..with the ears their may be little chunks of the skin that look 'tattered.' All in which NEED to be treated by a Vet. to get them cleared up & to be free from infection. Another good way to see if your hedge has mites is to get a dark cloth & rub it on the quills/ears.. look at it with a bright light & if you see anything white & slightly moving, YOU HEDGIE HAS MITES & GET IT TO THE VET. ASAP!
Don't confuse mites with dry skin though.. if you question it get them to a Vet. its the only way to be sure your hog has been successfully treated! Try treating yourself with a bit of vitamin E oil, or olive oil.. if the dryness doesnt go away, & or comes back you need to get them into see a Vet. fast. You will also have to disinfect EVERYTHING in their cage.. & you might as well throw away anything wooden, unless you can boil it.
Fungus: Fungus is generally found on/in the ears, a good way to tell if this is fungus is to look closely at them for dryness, redness, growths, or tattered edges. You MUST get this treated, as letting it go will result in infection, the ears to be slowly eaten away, or death. If fungus is growing on the quilled area of your hedgie it will again be very dry, could be red, swollen, having quill loss, ect, ect. If the fungus is on the fur part of your hedgie it will more than likely be dry, red, swollen, irritated, & missing fur.
Again, the only way to treat & be sure its taken care of is to take your hedgie to the Vet.